When Cameron Diaz appeared on Late Night with Jimmy Fallon earlier this week, she chatted with the host about the custom Stella McCartney gown she wore to the Costume Institute Gala Monday night. “That was a 22-pound dress…it was heavy,” she told Fallon. “It was rhinestones, all of those are, like, rhinestones…just strips and strips of rhinestones. Stella and I had talked about what we wanted to do, we went back and forth about the design of it…But she said, ‘Let’s do embroidery,’ and I was like, ‘Okay.’”

Diaz continued: “She sends me this e-mail on Friday, like, ‘Babe, your dress might be a little heavy,’ and I put it on on Saturday for the last alteration and it’s 30 pounds! We managed to cut eight pounds out of that dress. My knees are so sore today.” See the video after the cut.